Gaseous substances have been used to replace a liquid drained from a pressurized tank in order to maintain the pressure within the pressurized tank. However, due to the relatively high rates of gaseous substance often needed to replace the liquid drained from the pressurized tank, the velocity of the gaseous substance entering the pressurized tank can be considerably high. Diffusers have been used to try to reduce the velocity of gaseous substances entering a pressurized tank.